The present invention relates to integrated circuit devices and more particularly to data input-output circuits and methods for integrated circuit devices.
Integrated circuit devices, such as memory devices, are widely used in commercial and consumer applications. As integrated circuit devices continue to advance, high speed and high integration are generally desired. For such high-speed operation, the integrated circuit device may have an output unit with an open-drain structure.
An output unit with the open-drain structure has an output transistor where the drain port is floating. Either an NMOS or PMOS transistor can be used as the output transistor. When an NMOS transistor is used, the source port is connected to ground voltage (VSS) and the gate port receives real data to be output. In the open drain structure, the drain port of the output transistor is connected to a terminal voltage (Vterm) via a resistor. It will be understood that although an open-drain structure having an NMOS-type output transistor is described herein, PMOS devices also may be used.
Thus, when the real data is xe2x80x9c0xe2x80x9d, the output transistor is turned off. The voltage level of the output signal at the drain port of the output transistor becomes the terminal voltage (Vterm). When the real data is xe2x80x9c1xe2x80x9d, the output transistor is turned on. Thus, the voltage level of the output signal at the drain port of the output transistor is a value obtained by subtracting the voltage drop value across the resistor from the terminal voltage (Vterm). Thus, the output data of the open-drain output unit is defined only as logic xe2x80x9c1xe2x80x9d which is a state of consuming current, or as logic xe2x80x9c0xe2x80x9d which is a state of non-consuming current.
The open-drain output unit has a predetermined swing width to produce the data output of xe2x80x9c1xe2x80x9d or xe2x80x9c0xe2x80x9d. Thus, a predetermined positive current flows through the resistor, so that when the output data is xe2x80x9c1xe2x80x9d, a great amount of current may be consumed.
For example, when the resistance value of the resistor is 20xcexa9, approximately 50 mA of current flows from the terminal voltage (Vterm) to the ground voltage (VSS) to produce a swing width of about 1V. Thus, when 8 bits of output data having a data value of xe2x80x9c1xe2x80x9d are output, the open-drain output unit consumes a current of about 400 mA (=50 mA per bit). Unfortunately, such an increase in the amount of consumed current may decrease the efficiency and/or may shorten the life of the integrated circuit device.
It is therefore an object of the present invention to provide improved data input-output circuits and methods for integrated circuit devices.
It is another object of the present invention to provide data input-output circuits and methods that can reduce power consumption compared to conventional input-output circuits and methods.
These and other objects are provided, according to the present invention by outputting a plurality of bits if more of the plurality of bits are of a first logical value than a second logical value, and outputting the plurality of bits inverted if more of the plurality of bits are of the second logical value than the first logical value. An indicator also preferably is provided as to whether the plurality of bits or the plurality of bits inverted are output. Thus, for example, if more of the bits are of the logical value that causes high current consumption, the output bits are inverted so that the bits can be output with reduced current consumption. Upon receipt, the plurality of bits and the indicator are received. The plurality of bits is retained if the indicator is of a first value and the plurality of bits is inverted if the indicator is of a second value. Thus, the power consumption of the data input-output circuits may be reduced.
According to an aspect of the present invention, there is provided an output circuit for simultaneously outputting a plurality of data values A causing a current consumption of a, or B causing a current consumption of b which is more than the amount a. A plurality of data output units detect a plurality of real data values and generate temporary data corresponding to the respective real data in response to a control signal. A control unit generates the control signal which is activated according to the magnitude relation between the number of real data values A and the number of real data values B. The temporary data is the inverted real data when the number of real data values A is less than the number of real data values B, and the non-inverted real data when the number of real data values A is greater than the number of real data values B.
Preferably, the control unit includes a non-inversion detecting unit that detects the non-inverted data values of the real data and that generates a non-inversion detecting signal driven by the non-inverted data having the data values of B. An inversion detecting unit detects the inverted data values of the real data and generates an inversion detecting signal driven by the inverted data having the data values of A. A comparator compares the voltage level of the non-inversion detecting signal to the voltage level of the inversion detecting signal, and generates the control signal.
According to another aspect of the present invention, there is provided an input-output system for simultaneously inputting and outputting a plurality of real data having data values of A causing a current consumption of a, or B causing a current consumption of b which is more than the amount a. The input-output system includes an output device that detects the data values of the real data and provides transmission data corresponding to the real data, and an indication signal (indicator) to indicate the relationship between the real data and the transmission data. An input device receives the transmission data and the indication signal and provides input data, whose relationship with the transmission data is determined by the indication signal, to an internal circuit. The transmission data is the inverted real data when the number of real data values having the data value of A is less than the number of real data values having the data value of B, and the non-inverted real data when the number of real data values having the data value of A is greater than the number of real data values having the data value of B. The input data has the same data value as the real data.
According to still another aspect of the present invention, there is provided an output device for simultaneously outputting a plurality of data. The output device includes a data storage unit that stores predetermined real data and provides a plurality of real data in an output mode. An output circuit receives the real data and generates temporary data according to the data values of the real data. The temporary data is the inverted real data when the number of real data values having a data value of A causing a current consumption of a is less than the number of real data values having a data value of B causing a current consumption of b that is more than the current amount a, and the non-inverted real data when the number of real data values having the data value of A is greater than the number of real data values having the data value of B.
According to method aspects of the present invention, there is provided a method of simultaneously outputting a plurality of data having a data value of A consuming a current amount of a, or B consuming a current amount of b which is more than the amount of a. This method comprises the steps of sensing the data values of a plurality of real data; comparing the number (m) of real data having the data value of A to the number (n) of real data having the data value of B; generating temporary data by inverting the real data when the number (m) is greater than the number (n), and by non-inverting the real data when the number (m) is less than the number (n); and generating an indication signal for indicating the correlation between the temporary data and the real data.
According to other method aspects of the present invention, there is provided a data input and output method having an input and output system having an input/output device for simultaneously inputting/outputting a plurality of data having a data value of A consuming a current amount of a, or B consuming a current amount of b which is more than the amount of a. This method preferably comprises the steps of detecting the data values of a plurality of real data; comparing the number (m) of real data having the data value of A to the number (n) of real data having the data value of B; generating temporary data by inverting the real data when the number (m) is less than the number (n), and by non-inverting the real data when the number (m) is greater than or equal to the number (n); generating a control signal for indicating the correlation between the temporary data and the real data; and generating predetermined input data whose correlation with the temporary data is determined in response to the control signal. The input data has the same data value as the real data.
According to the present invention, when the number of data values causing large consumption of current is more than the number of data values causing a small consumption of current, the values of output data are inverted and output. The amount of current consumed therefore may be reduced. The reduction of the amount of current consumed can provide an increase in the efficiency and/or the life of an integrated circuit using the present invention.